Field of the Invention
The present invention relates to ink jet printers of the type having a print head carrying a plurality of individually controlled ink delivery channels, each channel having an ink drop ejection transducer and ending in a nozzle having an outlet orifice, with the orifices typically arranged in a row that extends transversely to a row printing direction.
In modern ink jet printers, high resolution is made possible by disposing the nozzle orifices very close together. This requires that the channels themselves be disposed close together and, as a result, dynamic forces, or excitations, exerted on one nozzle transducer generate lower level forces at adjacent transducers, a phenomenon known as crosstalk and representative of the level of signal interference between one transducer and neighboring transducers. This, of course, has adverse effects on the quality of the resulting image. Typically, these transducers are piezoelectric devices.
Various techniques for eliminating or minimizing crosstalk which have been proposed involve more or less complex modifications of the print head structure and notably the transducer, the fluid paths, or selected structural parameters of the print head. These solutions have either provided limited operating improvements or are costly and complex to implement. One reason that significant improvements have been elusive is that any modification of one parameter invariably influences other parameters in an unpredictable manner,
Further, in a print head of the type described above, all of the ejection transducers are connected to a single source of a driving voltage which imposes an excitation voltage across each transducer which is to be actuated, or "fired". Since all of the transducers are connected electrically in parallel with the driving voltage, the resulting excitation voltage across each connected transducer tends to decrease as the number of transducers fired at a given time increases. A decrease in this voltage results in a corresponding decrease in the velocity with which each ink drop is ejected and the size of the dot formed by each ink jet droplet. This represents another type of crosstalk which adversely affects print quality.